Chlorprothixene and Atenolol: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 15, 2026 · Source data updated Jul 11, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Atenolol
Chlorprothixene
No brand names on record
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
Taking atenolol with chlorprothixene may cause the effects of both drugs to add up. Atenolol is a beta blocker that lowers your blood pressure and slows your heart rate. Chlorprothixene is an older medicine used for mental health conditions that can also lower blood pressure. Together, they may each slow the other's breakdown in your body, so both can build up a bit and act stronger.
In real life, this could mean feeling dizzy, lightheaded, or faint, especially when you stand up. The good news is that this is based on theory rather than strong reports, and your care team can manage it easily by watching how you feel and adjusting a dose if needed. Let them know if you feel dizzy.
Effect: Additive hypotension and/or enhanced phenothiazine-type (thioxanthene) effects.
- Mechanism: Proposed mutual inhibition of metabolism, causing increased exposure to both agents, plus additive pharmacodynamic BP-lowering effects. Neither drug is a prodrug, so exposure increases translate to enhanced effect.
- Direction/magnitude: Increased effect of both; magnitude not quantified.
- Onset: Rapid.
- Evidence: Theoretical; extrapolated from other phenothiazine/beta-blocker pairs, not reported specifically for this combination.
- Management: Monitor BP, heart rate, and for excessive sedation or orthostasis. Reduce dose of one or both agents if enhanced effects emerge.
What happens
Hypotension and/or phenothiazine toxicity
Interaction Deep Dive
While this has not been described specifically for the combination of chlorprothixene and atenolol, compounds related to phenothiazines and beta blocking agents have been shown to potentiate one another's effects123. Each may impair the metabolism of the other, resulting in additive effects from both drugs.
Why it happens (mechanism)
Mutual inhibition of metabolism
How to manage this interaction
Keep taking both medicines as prescribed unless your prescriber tells you otherwise. This interaction is usually manageable with attention.
- Your care team may monitor your blood pressure and heart rate more closely, especially when you first combine these drugs.
- If enhanced effects appear, the dose of one or both may be adjusted and individualized by your care team.
- Tell your pharmacist or doctor if you feel dizzy, lightheaded, faint, unusually sleepy, or notice a slow heartbeat.
- Stand up slowly to lower your risk of dizziness.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Chlorprothixene and Atenolol together?
Combining atenolol and chlorprothixene can add up to lower blood pressure and stronger effects from both, so watch for dizziness and let your care team monitor you; they can adjust a dose if needed. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Chlorprothixene and Atenolol interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "rapid". Effects can appear quickly, often within about 24 hours of combining the drugs.
How is the Chlorprothixene and Atenolol interaction managed?
Keep taking both medicines as prescribed unless your prescriber tells you otherwise. This interaction is usually manageable with attention. Your care team may monitor your blood pressure and heart rate more closely, especially when you first combine these drugs. If enhanced effects appear, the dose of one or both may be adjusted and individualized by your care team. Tell your pharmacist or doctor… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
Questions for your pharmacist
- Does my dose of Chlorprothixene or Atenolol need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there anything you'd monitor while I'm on both?
References (3)
- Peet M, Middlemiss SN, & Yates RA: Propranolol in schizophrenia. II. Clinical and biochemical aspects of combining propranolol with chlorpromazine. Br J Psychiatry 1981; 138:112-117. PubMed
- Vestal RE, Kornhauser DM, Hollifield JW, et al: Inhibition of propranolol metabolism by chlorpromazine. Clin Pharmacol Ther 1979; 25:19-24. PubMed
- Greendyke RM & Gulya A: Effect of pindolol administration on serum levels of thioridazine, haloperidol, phenytoin, and phenobarbital. J Clin Psychiatry 1988; 49:105-107.
Keep reading about Atenolol
Keep reading about Chlorprothixene
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